[Desktop_printing] Update of the Printing Summit Agenda

Michael Sweet mike at easysw.com
Wed Jan 11 17:46:24 PST 2006

Ralph Giles wrote:
> On Wed, Jan 11, 2006 at 05:39:12PM -0500, Michael Sweet wrote:
>> No, I mean the alpha masking support built into Level 3 PostScript, and
>> support for 16bpp color data that has been in PostScript since the
>> Level 1 days.
> Can you point me at some documentation for this? As far as I'm aware, 
> PostScript supports only 1,2,4,8, and 12 bits-per-channel in images
> and either 1 bit alpha (type3 and imagemask) or binary color-key (type4) 
> masking.

The MaskDict entry in a Type 3 image defines the mask image, which
for InterleaveType 1 requires you to provide an alpha mask with the
same depth as the color data in the main image.  See pages 303 to
307 of the PostScript Language Reference Manual, Third Edition.
(This *does* work, I use it in HTMLDOC's Level 3 output...)

You are correct about the 12bpp part, though - I forgot that Adobe
had limited it... :(  Anyways, 12bpp is still deep enough for most
devices (I only know of some very-high-end x-ray imaging devices
that can claim better accuracy...), so we can still do high-quality
PDF to PostScript conversion for Level 3 devices.

Michael Sweet, Easy Software Products           mike at easysw dot com
Internet Printing and Publishing Software        http://www.easysw.com

More information about the Printing-summit mailing list